Final answer:
The Himalayas is the mountain range that crosses through southern Asia, forming a natural barrier between India and China.
Step-by-step explanation:
The mountain range that crosses through southern Asia is the Himalayas. The Himalayas form a natural barrier between India and China and stretch through countries such as Nepal and Bhutan. These mountains continue to increase in elevation due to tectonic action, with some peaks reaching the highest elevations in the world, including Mount Everest and K2.